the iron lost from absorption by the lining or in dumping the bottom is small in proportion to the amount treated. In an iron foundry or a small Bessemer plant, the cupola works only a short time, and a considerable proportion of the iron is absorbed by the lining, while another large percentage is lost in scrap. In a standard Bessemer cupola the loss in metallic iron is only one-half of one per cent., while in intermittent cupola work it will be far above this figure.
In the standard converter with low-silicon pig-iron, the total loss is about 8 per cent., of which only 3 per cent, is metallic iron, about one-half of this (1.8 per cent.) being carried away as oxide in the slag and the remainder lost in shot and splashes. In the small converter it is necessary to use much higher silicon, and this gives a higher loss. A rough estimate of the waste under the two different methods is given'herewith.
Per cent, of metal.
Standard practice ; bottom blast. Small vessels ; side blast.
Cupolas : Vessels : Metalloids ............ 1.5 0.5 5.0 1.8 1.3 2.0 3.0 7.0 4.0 4.0
Iron ....... . .
Slag (as oxide) ...... ,
Shot and splashes. . .
Total 10.0 20.0
The increased loss will cost about $2 per ton, but this is less than, it would cost for fuel in a small open-hearth furnace running irjtermittently, to 'say nothing of the waste that will take place in open-hearth work. Small converters will give a very hot steel, although sometimes it is found necessary to add f erro-silicon at the end of the operation and continue blowing in order to get a higher temperature.
The disadvantages of the small converters are indicated by the slow progress in their introduction and the discontinuance of operation in plants already built. . The Clapp-Griffiths process once